1. Field of the Invention
The present invention relates generally to systems and methods for propulsion, and, more specifically, the present invention relates to control systems for large pulsed power applications that use multiple pulsed alternators in synchronization.
2. Description of the Background
Multiple pulsed alternators have been applied to a variety of systems including electromagnetic aircraft launchers, electromagnetic rail guns, and many pulsed power systems used for laboratory experiments.
High current pulses can be provided from several types of pulse sources such as a capacitor bank or rotating electric machines. The pulsed alternator (PA) is considered to be the most effective and power dense type of pulse source. A basic pulsed alternator system designed around a single pulsed alternator requires several other components as shown in FIG. 1.
The pulsed alternator PA, field power controller FPC and load converter LC for a four-phase, four-pole poled alternator are the major components for the system shown in FIG. 1. The four-phase or four-pole machine pictured in the accompanying figures is exemplary only, and the present invention is not limited to any particular number of phases/poles. The pulsed alternator is designed to store kinetic energy that will be converted to an ac electric energy pulse by the operation of the pulsed alternator and the load converter.
Previous controls used for multiple pulsed alternator applications used only open loop, feed forward controllers with empirically developed algorithms. This control approach is based on the fact that a pulse discharge event lasts only about 5 to 10 milliseconds (ms) and a limited number of alternator voltage cycles occur during the discharge limiting the control bandwidth.
It is understood that it is necessary to synchronize the pulsed alternators in multiple parallel-connected machines prior to a discharge to ensure that the load current will share equally and large transient and unequal torque reaction will not occur during discharges. In these systems, synchronization concepts have been based only on equalizing the initial speeds of the pulsed alternators.